1. Field of the Invention
This invention relates to a self-holding type push switch with heart-shaped cam, which permits easy assembly by first forming a spring member positively engaging a hook rod.
2. Prior Art
It is widely known that a push switch having a slider means slidably received in a switch case can be provided with a so-called heart type cam. The cam is located on the slider means and is heart-shaped in section in such a manner that a hook rod pivotably supported on the switch case and bent at the end in a hook shape is adapted to trace the outer circumference of the cam. The end of the hook rod travels around the outer circumference of the cam as the slider means moves, to bring the rod into and out of engagement with the recess of the heart-shaped cam, and positions the slider means at a predetermined position along its sliding direction.
In order to make it possible for the hook rod to exactly travel around the cam, it is necessary to constantly urge a spring member, for example, a plate spring, against the slider means. However, because the hook rod and the spring member were conventionally provided in the form of separate parts easily disengaged and free to move with respect to each other, it was a general practice in assembling to bring one end of the hook rod into engagement with an engagement hole formed in the switch case by use of pincers, insert a plate spring having an end bent in an L-shape into the switch case through a slit in the bottom of the switch case, bring the spring into contact with the hook rod and then fix the end of the spring, for example, by an adhesive, to the outside bottom of the switch case.
Accordingly, mounting the hook rod and the spring member, and assembly of the switch, was troublesome work. Assembly was difficult and required use of assembling tools such as pincers, with the result that the assembly was not very workable, and the number of assembling steps and working time was increased.
In addition, since the hook rod and spring member were handled as parts independent from each other, the added number of parts and the control of parts was also troublesome.